In BGP, routing policies are used to control the flow of routing information between BGP peers.
Option C suggests that import policies are applied after the RIB-In table. This is correct because import policies in BGP are applied to routes that are received from a BGP peer, before they are installed in the local BGP Routing Information Base (RIB-In). The RIB-In is a database that stores all the routes that are received from all peers.
Option D suggests that export policies are applied after the RIB-Local table. This is correct because export policies in BGP are applied to routes that are being advertised to a BGP peer, after they have been selected from the local BGP Routing Information Base (RIB-Local). The RIB-Local is a database that stores all the routes that the local router is using.

A) On R1, enable Level 1 on the ge-0/0/1 interface. In IS-IS, both levels (Level 1 and Level 2) are enabled by default when you enable IS-IS on an interface1. Level 1 systems route within an area.
If the destination is outside an area, Level 1 systems route toward a Level 2 system. Therefore, enabling Level 1 on the ge-0/0/1 interface on R1 would allow packets to reach from R1 to R3.
D) On R3 enable Level 1 on the ge-0/0/4 interface Similarly, enabling Level 1 on the ge-0/0/4 interface on R3 would allow packets to reach from R1 to R3. These explanations are based on the IS-IS configuration documents and learning resources available at Juniper Networks1 and Cisco.

Option A suggests that the MTU is not at least 1492 bytes. This is correct because IS-IS requires a minimum MTU of 1492 bytes to establish adjacencies. If the MTU is less than this, IS-IS adjacencies will not be established.
Option D suggests that the lo0 interface is not included as an IS-IS interface. This is also correct because the loopback interface (lo0) is typically used as the router ID in IS-IS. If the loopback interface is not included in IS-IS, it could prevent IS-IS adjacencies from being established.